By way of introduction, the use of random delays, also known as random wait-states, is often proposed as a generic counter-measure against side-channel analysis and fault attacks by stalling a CPU during execution of embedded software. The efficiency of a random delay triggering scheme improves as the variance of the random wait-states increases. However, systems typically incorporate random wait-states that are uniformly distributed.
The following references are also believed to represent the state of the art:
U.S. Pat. No. 6,167,553 to Dent;
U.S. Pat. No. 6,785,389 to Sella, et al.;
US Published Patent Application 2003/0085286 of Kelley, et al.;
US Published Patent Application 2004/0076293 of Smeets, et al.;
US Published Patent Application 2004/0205095 of Gressel, et al.;
US Published Patent Application 2006/0161610 of Goettfert, et al.;
Article entitled “Efficient Use of Random Delays” by Olivier Benoit and Michael Tunstall of Royal Holloway, University of London; and
Chapter 6 of Handbook of Applied Cryptography (CRC Press Series on Discrete Mathematics and Its Applications) by Alfred J. Menezes, Paul C. van Oorschot, and Scott A. Vanstone.
The disclosures of all references mentioned above and throughout the present specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.